utls/u_common.go

// Copyright 2017 Google Inc. 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/hmac"
	"crypto/sha512"
	"encoding/json"
	"errors"
	"fmt"
	"hash"
	"log"

	"github.com/refraction-networking/utls/internal/helper"
	"golang.org/x/crypto/cryptobyte"
)

// Naming convention:
// Unsupported things are prefixed with "Fake"
// Things, supported by utls, but not crypto/tls' are prefixed with "utls"
// Supported things, that have changed their ID are prefixed with "Old"
// Supported but disabled things are prefixed with "Disabled". We will _enable_ them.

// TLS handshake message types.
const (
	utlsTypeEncryptedExtensions uint8 = 8 // implemention incomplete by crypto/tls
	// https://datatracker.ietf.org/doc/html/rfc8879#section-7.2
	utlsTypeCompressedCertificate uint8 = 25
)

// TLS
const (
	extensionNextProtoNeg uint16 = 13172 // not IANA assigned. Removed by crypto/tls since Nov 2019

	utlsExtensionPadding              uint16 = 21
	utlsExtensionExtendedMasterSecret uint16 = 23    // https://tools.ietf.org/html/rfc7627
	utlsExtensionCompressCertificate  uint16 = 27    // https://datatracker.ietf.org/doc/html/rfc8879#section-7.1
	utlsExtensionApplicationSettings  uint16 = 17513 // not IANA assigned
	utlsFakeExtensionCustom           uint16 = 1234  // not IANA assigned, for ALPS

	// extensions with 'fake' prefix break connection, if server echoes them back
	fakeExtensionEncryptThenMAC       uint16 = 22
	fakeExtensionTokenBinding         uint16 = 24
	fakeExtensionDelegatedCredentials uint16 = 34
	fakeExtensionPreSharedKey         uint16 = 41
	fakeOldExtensionChannelID         uint16 = 30031 // not IANA assigned
	fakeExtensionChannelID            uint16 = 30032 // not IANA assigned
)

const (
	OLD_TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256   = uint16(0xcc13)
	OLD_TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 = uint16(0xcc14)

	DISABLED_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 = uint16(0xc024)
	DISABLED_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384   = uint16(0xc028)
	DISABLED_TLS_RSA_WITH_AES_256_CBC_SHA256         = uint16(0x003d)

	FAKE_OLD_TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256 = uint16(0xcc15) // we can try to craft these ciphersuites
	FAKE_TLS_DHE_RSA_WITH_AES_128_GCM_SHA256           = uint16(0x009e) // from existing pieces, if needed

	FAKE_TLS_DHE_RSA_WITH_AES_128_CBC_SHA    = uint16(0x0033)
	FAKE_TLS_DHE_RSA_WITH_AES_256_CBC_SHA    = uint16(0x0039)
	FAKE_TLS_RSA_WITH_RC4_128_MD5            = uint16(0x0004)
	FAKE_TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 = uint16(0x009f)
	FAKE_TLS_DHE_DSS_WITH_AES_128_CBC_SHA    = uint16(0x0032)
	FAKE_TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 = uint16(0x006b)
	FAKE_TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 = uint16(0x0067)
	FAKE_TLS_EMPTY_RENEGOTIATION_INFO_SCSV   = uint16(0x00ff)

	// https://docs.microsoft.com/en-us/dotnet/api/system.net.security.tlsciphersuite?view=netcore-3.1
	FAKE_TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA = uint16(0xc008)
)

// Other things
const (
	fakeRecordSizeLimit uint16 = 0x001c
)

// newest signatures
var (
	FakePKCS1WithSHA224 SignatureScheme = 0x0301
	FakeECDSAWithSHA224 SignatureScheme = 0x0303

	FakeSHA1WithDSA   SignatureScheme = 0x0202
	FakeSHA256WithDSA SignatureScheme = 0x0402

	// fakeEd25519 = SignatureAndHash{0x08, 0x07}
	// fakeEd448 = SignatureAndHash{0x08, 0x08}
)

// fake curves(groups)
var (
	FakeFFDHE2048 = uint16(0x0100)
	FakeFFDHE3072 = uint16(0x0101)
)

// https://tools.ietf.org/html/draft-ietf-tls-certificate-compression-04
type CertCompressionAlgo uint16

const (
	CertCompressionZlib   CertCompressionAlgo = 0x0001
	CertCompressionBrotli CertCompressionAlgo = 0x0002
	CertCompressionZstd   CertCompressionAlgo = 0x0003
)

const (
	PskModePlain uint8 = pskModePlain
	PskModeDHE   uint8 = pskModeDHE
)

type ClientHelloID struct {
	Client string

	// Version specifies version of a mimicked clients (e.g. browsers).
	// Not used in randomized, custom handshake, and default Go.
	Version string

	// Seed is only used for randomized fingerprints to seed PRNG.
	// Must not be modified once set.
	Seed *PRNGSeed

	// Weights are only used for randomized fingerprints in func
	// generateRandomizedSpec(). Must not be modified once set.
	Weights *Weights
}

func (p *ClientHelloID) Str() string {
	return fmt.Sprintf("%s-%s", p.Client, p.Version)
}

func (p *ClientHelloID) IsSet() bool {
	return (p.Client == "") && (p.Version == "")
}

const (
	// clients
	helloGolang           = "Golang"
	helloRandomized       = "Randomized"
	helloRandomizedALPN   = "Randomized-ALPN"
	helloRandomizedNoALPN = "Randomized-NoALPN"
	helloCustom           = "Custom"
	helloFirefox          = "Firefox"
	helloChrome           = "Chrome"
	helloIOS              = "iOS"
	helloAndroid          = "Android"
	helloEdge             = "Edge"
	helloSafari           = "Safari"
	hello360              = "360Browser"
	helloQQ               = "QQBrowser"

	// versions
	helloAutoVers = "0"
)

type ClientHelloSpec struct {
	CipherSuites       []uint16       // nil => default
	CompressionMethods []uint8        // nil => no compression
	Extensions         []TLSExtension // nil => no extensions

	TLSVersMin uint16 // [1.0-1.3] default: parse from .Extensions, if SupportedVersions ext is not present => 1.0
	TLSVersMax uint16 // [1.2-1.3] default: parse from .Extensions, if SupportedVersions ext is not present => 1.2

	// GreaseStyle: currently only random
	// sessionID may or may not depend on ticket; nil => random
	GetSessionID func(ticket []byte) [32]byte

	// TLSFingerprintLink string // ?? link to tlsfingerprint.io for informational purposes
}

// ReadCipherSuites is a helper function to construct a list of cipher suites from
// a []byte into []uint16.
//
// example: []byte{0x13, 0x01, 0x13, 0x02, 0x13, 0x03} => []uint16{0x1301, 0x1302, 0x1303}
func (chs *ClientHelloSpec) ReadCipherSuites(b []byte) error {
	cipherSuites := []uint16{}
	s := cryptobyte.String(b)
	for !s.Empty() {
		var suite uint16
		if !s.ReadUint16(&suite) {
			return errors.New("unable to read ciphersuite")
		}
		cipherSuites = append(cipherSuites, unGREASEUint16(suite))
	}
	chs.CipherSuites = cipherSuites
	return nil
}

// ReadCompressionMethods is a helper function to construct a list of compression
// methods from a []byte into []uint8.
func (chs *ClientHelloSpec) ReadCompressionMethods(compressionMethods []byte) error {
	chs.CompressionMethods = compressionMethods
	return nil
}

// ReadTLSExtensions is a helper function to construct a list of TLS extensions from
// a byte slice into []TLSExtension.
//
// If keepPSK is not set, the PSK extension will cause an error.
func (chs *ClientHelloSpec) ReadTLSExtensions(b []byte, allowBluntMimicry bool) error {
	extensions := cryptobyte.String(b)
	for !extensions.Empty() {
		var extension uint16
		var extData cryptobyte.String
		if !extensions.ReadUint16(&extension) {
			return fmt.Errorf("unable to read extension ID")
		}
		if !extensions.ReadUint16LengthPrefixed(&extData) {
			return fmt.Errorf("unable to read data for extension %x", extension)
		}

		extWriter := ExtensionIDToExtension(extension)
		if extWriter != nil {
			if extension == extensionSupportedVersions {
				chs.TLSVersMin = 0
				chs.TLSVersMax = 0
			}
			if _, err := extWriter.Write(extData); err != nil {
				return err
			}

			chs.Extensions = append(chs.Extensions, extWriter)
		} else {
			if allowBluntMimicry {
				chs.Extensions = append(chs.Extensions, &GenericExtension{extension, extData})
			} else {
				return fmt.Errorf("unsupported extension %d", extension)
			}
		}
	}
	return nil
}

func (chs *ClientHelloSpec) AlwaysAddPadding() {
	alreadyHasPadding := false
	for _, ext := range chs.Extensions {
		if _, ok := ext.(*UtlsPaddingExtension); ok {
			alreadyHasPadding = true
			break
		}
		if _, ok := ext.(*FakePreSharedKeyExtension); ok {
			alreadyHasPadding = true // PSK must be last, so we don't need to add padding
			break
		}
	}
	if !alreadyHasPadding {
		chs.Extensions = append(chs.Extensions, &UtlsPaddingExtension{GetPaddingLen: BoringPaddingStyle})
	}
}

// Import TLS ClientHello data from client.tlsfingerprint.io:8443
//
// data is a map of []byte with following keys:
// - cipher_suites: [10, 10, 19, 1, 19, 2, 19, 3, 192, 43, 192, 47, 192, 44, 192, 48, 204, 169, 204, 168, 192, 19, 192, 20, 0, 156, 0, 157, 0, 47, 0, 53]
// - compression_methods: [0] => null
// - extensions: [10, 10, 255, 1, 0, 45, 0, 35, 0, 16, 68, 105, 0, 11, 0, 43, 0, 18, 0, 13, 0, 0, 0, 10, 0, 27, 0, 5, 0, 51, 0, 23, 10, 10, 0, 21]
// - pt_fmts (ec_point_formats): [1, 0] => len: 1, content: 0x00
// - sig_algs （signature_algorithms): [0, 16, 4, 3, 8, 4, 4, 1, 5, 3, 8, 5, 5, 1, 8, 6, 6, 1] => len: 16, content: 0x0403, 0x0804, 0x0401, 0x0503, 0x0805, 0x0501, 0x0806, 0x0601
// - supported_versions: [10, 10, 3, 4, 3, 3] => 0x0a0a, 0x0304, 0x0303 (GREASE, TLS 1.3, TLS 1.2)
// - curves (named_groups, supported_groups): [0, 8, 10, 10, 0, 29, 0, 23, 0, 24] => len: 8, content: GREASE, 0x001d, 0x0017, 0x0018
// - alpn: [0, 12, 2, 104, 50, 8, 104, 116, 116, 112, 47, 49, 46, 49] => len: 12, content: h2, http/1.1
// - key_share: [10, 10, 0, 1, 0, 29, 0, 32] => {group: 0x0a0a, len:1}, {group: 0x001d, len:32}
// - psk_key_exchange_modes: [1] => psk_dhe_ke(0x01)
// - cert_compression_algs: [2, 0, 2] => brotli (0x0002)
// - record_size_limit: [0, 255] => 255
//
// TLSVersMin/TLSVersMax are set to 0 if supported_versions is present.
// To prevent conflict, they should be set manually if needed BEFORE calling this function.
func (chs *ClientHelloSpec) ImportTLSClientHello(data map[string][]byte) error {
	var tlsExtensionTypes []uint16
	var err error

	if data["cipher_suites"] == nil {
		return errors.New("cipher_suites is required")
	}
	chs.CipherSuites, err = helper.Uint8to16(data["cipher_suites"])
	if err != nil {
		return err
	}

	if data["compression_methods"] == nil {
		return errors.New("compression_methods is required")
	}
	chs.CompressionMethods = data["compression_methods"]

	if data["extensions"] == nil {
		return errors.New("extensions is required")
	}
	tlsExtensionTypes, err = helper.Uint8to16(data["extensions"])
	if err != nil {
		return err
	}

	for _, extType := range tlsExtensionTypes {
		extension := ExtensionIDToExtension(extType)
		if extension == nil {
			log.Printf("[Warning] Unsupported extension %d added as a &GenericExtension without Data", extType)
			chs.Extensions = append(chs.Extensions, &GenericExtension{extType, []byte{}})
		} else {
			switch extType {
			case extensionSupportedPoints:
				if data["pt_fmts"] == nil {
					return errors.New("pt_fmts is required")
				}
				_, err = extension.Write(data["pt_fmts"])
				if err != nil {
					return err
				}
			case extensionSignatureAlgorithms:
				if data["sig_algs"] == nil {
					return errors.New("sig_algs is required")
				}
				_, err = extension.Write(data["sig_algs"])
				if err != nil {
					return err
				}
			case extensionSupportedVersions:
				chs.TLSVersMin = 0
				chs.TLSVersMax = 0

				if data["supported_versions"] == nil {
					return errors.New("supported_versions is required")
				}

				// need to add uint8 length prefix
				fixedData := make([]byte, len(data["supported_versions"])+1)
				fixedData[0] = uint8(len(data["supported_versions"]) & 0xff)
				copy(fixedData[1:], data["supported_versions"])
				_, err = extension.Write(fixedData)
				if err != nil {
					return err
				}
			case extensionSupportedCurves:
				if data["curves"] == nil {
					return errors.New("curves is required")
				}

				_, err = extension.Write(data["curves"])
				if err != nil {
					return err
				}
			case extensionALPN:
				if data["alpn"] == nil {
					return errors.New("alpn is required")
				}

				_, err = extension.Write(data["alpn"])
				if err != nil {
					return err
				}
			case extensionKeyShare:
				if data["key_share"] == nil {
					return errors.New("key_share is required")
				}

				// need to add (zero) data per each key share, [10, 10, 0, 1] => [10, 10, 0, 1, 0]
				fixedData := make([]byte, 0)
				for i := 0; i < len(data["key_share"]); i += 4 {
					fixedData = append(fixedData, data["key_share"][i:i+4]...)
					for j := 0; j < int(data["key_share"][i+3]); j++ {
						fixedData = append(fixedData, 0)
					}
				}
				// add uint16 length prefix
				fixedData = append([]byte{uint8(len(fixedData) >> 8), uint8(len(fixedData) & 0xff)}, fixedData...)

				_, err = extension.Write(fixedData)
				if err != nil {
					return err
				}
			case extensionPSKModes:
				if data["psk_key_exchange_modes"] == nil {
					return errors.New("psk_key_exchange_modes is required")
				}

				// need to add uint8 length prefix
				fixedData := make([]byte, len(data["psk_key_exchange_modes"])+1)
				fixedData[0] = uint8(len(data["psk_key_exchange_modes"]) & 0xff)
				copy(fixedData[1:], data["psk_key_exchange_modes"])
				_, err = extension.Write(fixedData)
				if err != nil {
					return err
				}
			case utlsExtensionCompressCertificate:
				if data["cert_compression_algs"] == nil {
					return errors.New("cert_compression_algs is required")
				}

				// need to add uint8 length prefix
				fixedData := make([]byte, len(data["cert_compression_algs"])+1)
				fixedData[0] = uint8(len(data["cert_compression_algs"]) & 0xff)
				copy(fixedData[1:], data["cert_compression_algs"])
				_, err = extension.Write(fixedData)
				if err != nil {
					return err
				}
			case fakeRecordSizeLimit:
				if data["record_size_limit"] == nil {
					return errors.New("record_size_limit is required")
				}

				_, err = extension.Write(data["record_size_limit"]) // uint16 as []byte
				if err != nil {
					return err
				}
			case utlsExtensionApplicationSettings:
				// TODO: tlsfingerprint.io should record/provide application settings data
				extension.(*ApplicationSettingsExtension).SupportedProtocols = []string{"h2"}
			case fakeExtensionPreSharedKey:
				log.Printf("[Warning] PSK extension added without data")
			default:
				if !isGREASEUint16(extType) {
					log.Printf("[Warning] extension %d added without data", extType)
				} /*else {
					log.Printf("[Warning] GREASE extension added but ID/Data discarded. They will be automatically re-GREASEd on ApplyPreset() call.")
				}*/
			}
			chs.Extensions = append(chs.Extensions, extension)
		}
	}
	return nil
}

func (chs *ClientHelloSpec) ImportTLSClientHelloFromJSON(jsonB []byte) error {
	var data map[string][]byte
	err := json.Unmarshal(jsonB, &data)
	if err != nil {
		return err
	}
	return chs.ImportTLSClientHello(data)
}

var (
	// HelloGolang will use default "crypto/tls" handshake marshaling codepath, which WILL
	// overwrite your changes to Hello(Config, Session are fine).
	// You might want to call BuildHandshakeState() before applying any changes.
	// UConn.Extensions will be completely ignored.
	HelloGolang = ClientHelloID{helloGolang, helloAutoVers, nil, nil}

	// HelloCustom will prepare ClientHello with empty uconn.Extensions so you can fill it with
	// TLSExtensions manually or use ApplyPreset function
	HelloCustom = ClientHelloID{helloCustom, helloAutoVers, nil, nil}

	// HelloRandomized* randomly adds/reorders extensions, ciphersuites, etc.
	HelloRandomized       = ClientHelloID{helloRandomized, helloAutoVers, nil, nil}
	HelloRandomizedALPN   = ClientHelloID{helloRandomizedALPN, helloAutoVers, nil, nil}
	HelloRandomizedNoALPN = ClientHelloID{helloRandomizedNoALPN, helloAutoVers, nil, nil}

	// The rest will will parrot given browser.
	HelloFirefox_Auto = HelloFirefox_105
	HelloFirefox_55   = ClientHelloID{helloFirefox, "55", nil, nil}
	HelloFirefox_56   = ClientHelloID{helloFirefox, "56", nil, nil}
	HelloFirefox_63   = ClientHelloID{helloFirefox, "63", nil, nil}
	HelloFirefox_65   = ClientHelloID{helloFirefox, "65", nil, nil}
	HelloFirefox_99   = ClientHelloID{helloFirefox, "99", nil, nil}
	HelloFirefox_102  = ClientHelloID{helloFirefox, "102", nil, nil}
	HelloFirefox_105  = ClientHelloID{helloFirefox, "105", nil, nil}

	HelloChrome_Auto        = HelloChrome_106_Shuffle
	HelloChrome_58          = ClientHelloID{helloChrome, "58", nil, nil}
	HelloChrome_62          = ClientHelloID{helloChrome, "62", nil, nil}
	HelloChrome_70          = ClientHelloID{helloChrome, "70", nil, nil}
	HelloChrome_72          = ClientHelloID{helloChrome, "72", nil, nil}
	HelloChrome_83          = ClientHelloID{helloChrome, "83", nil, nil}
	HelloChrome_87          = ClientHelloID{helloChrome, "87", nil, nil}
	HelloChrome_96          = ClientHelloID{helloChrome, "96", nil, nil}
	HelloChrome_100         = ClientHelloID{helloChrome, "100", nil, nil}
	HelloChrome_102         = ClientHelloID{helloChrome, "102", nil, nil}
	HelloChrome_106_Shuffle = ClientHelloID{helloChrome, "106", nil, nil} // beta: shuffler enabled starting from 106

	HelloIOS_Auto = HelloIOS_14
	HelloIOS_11_1 = ClientHelloID{helloIOS, "111", nil, nil} // legacy "111" means 11.1
	HelloIOS_12_1 = ClientHelloID{helloIOS, "12.1", nil, nil}
	HelloIOS_13   = ClientHelloID{helloIOS, "13", nil, nil}
	HelloIOS_14   = ClientHelloID{helloIOS, "14", nil, nil}

	HelloAndroid_11_OkHttp = ClientHelloID{helloAndroid, "11", nil, nil}

	HelloEdge_Auto = HelloEdge_85 // HelloEdge_106 seems to be incompatible with this library
	HelloEdge_85   = ClientHelloID{helloEdge, "85", nil, nil}
	HelloEdge_106  = ClientHelloID{helloEdge, "106", nil, nil}

	HelloSafari_Auto = HelloSafari_16_0
	HelloSafari_16_0 = ClientHelloID{helloSafari, "16.0", nil, nil}

	Hello360_Auto = Hello360_7_5 // Hello360_11_0 seems to be incompatible with this library
	Hello360_7_5  = ClientHelloID{hello360, "7.5", nil, nil}
	Hello360_11_0 = ClientHelloID{hello360, "11.0", nil, nil}

	HelloQQ_Auto = HelloQQ_11_1
	HelloQQ_11_1 = ClientHelloID{helloQQ, "11.1", nil, nil}
)

type Weights struct {
	Extensions_Append_ALPN                             float64
	TLSVersMax_Set_VersionTLS13                        float64
	CipherSuites_Remove_RandomCiphers                  float64
	SigAndHashAlgos_Append_ECDSAWithSHA1               float64
	SigAndHashAlgos_Append_ECDSAWithP521AndSHA512      float64
	SigAndHashAlgos_Append_PSSWithSHA256               float64
	SigAndHashAlgos_Append_PSSWithSHA384_PSSWithSHA512 float64
	CurveIDs_Append_X25519                             float64
	CurveIDs_Append_CurveP521                          float64
	Extensions_Append_Padding                          float64
	Extensions_Append_Status                           float64
	Extensions_Append_SCT                              float64
	Extensions_Append_Reneg                            float64
	Extensions_Append_EMS                              float64
	FirstKeyShare_Set_CurveP256                        float64
	Extensions_Append_ALPS                             float64
}

// Do not modify them directly as they may being used. If you
// want to use your custom weights, please make a copy first.
var DefaultWeights = Weights{
	Extensions_Append_ALPN:                             0.7,
	TLSVersMax_Set_VersionTLS13:                        0.4,
	CipherSuites_Remove_RandomCiphers:                  0.4,
	SigAndHashAlgos_Append_ECDSAWithSHA1:               0.63,
	SigAndHashAlgos_Append_ECDSAWithP521AndSHA512:      0.59,
	SigAndHashAlgos_Append_PSSWithSHA256:               0.51,
	SigAndHashAlgos_Append_PSSWithSHA384_PSSWithSHA512: 0.9,
	CurveIDs_Append_X25519:                             0.71,
	CurveIDs_Append_CurveP521:                          0.46,
	Extensions_Append_Padding:                          0.62,
	Extensions_Append_Status:                           0.74,
	Extensions_Append_SCT:                              0.46,
	Extensions_Append_Reneg:                            0.75,
	Extensions_Append_EMS:                              0.77,
	FirstKeyShare_Set_CurveP256:                        0.25,
	Extensions_Append_ALPS:                             0.33,
}

// based on spec's GreaseStyle, GREASE_PLACEHOLDER may be replaced by another GREASE value
// https://tools.ietf.org/html/draft-ietf-tls-grease-01
const GREASE_PLACEHOLDER = 0x0a0a

func isGREASEUint16(v uint16) bool {
	// First byte is same as second byte
	// and lowest nibble is 0xa
	return ((v >> 8) == v&0xff) && v&0xf == 0xa
}

func unGREASEUint16(v uint16) uint16 {
	if isGREASEUint16(v) {
		return GREASE_PLACEHOLDER
	} else {
		return v
	}
}

// utlsMacSHA384 returns a SHA-384 based MAC. These are only supported in TLS 1.2
// so the given version is ignored.
func utlsMacSHA384(key []byte) hash.Hash {
	return hmac.New(sha512.New384, key)
}

var utlsSupportedCipherSuites []*cipherSuite

func init() {
	utlsSupportedCipherSuites = append(cipherSuites, []*cipherSuite{
		{OLD_TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256, 32, 0, 12, ecdheRSAKA,
			suiteECDHE | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
		{OLD_TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256, 32, 0, 12, ecdheECDSAKA,
			suiteECDHE | suiteECSign | suiteTLS12, nil, nil, aeadChaCha20Poly1305},
	}...)
}

// EnableWeakCiphers allows utls connections to continue in some cases, when weak cipher was chosen.
// This provides better compatibility with servers on the web, but weakens security. Feel free
// to use this option if you establish additional secure connection inside of utls connection.
// This option does not change the shape of parrots (i.e. same ciphers will be offered either way).
// Must be called before establishing any connections.
func EnableWeakCiphers() {
	utlsSupportedCipherSuites = append(cipherSuites, []*cipherSuite{
		{DISABLED_TLS_RSA_WITH_AES_256_CBC_SHA256, 32, 32, 16, rsaKA,
			suiteTLS12, cipherAES, macSHA256, nil},

		{DISABLED_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384, 32, 48, 16, ecdheECDSAKA,
			suiteECDHE | suiteECSign | suiteTLS12 | suiteSHA384, cipherAES, utlsMacSHA384, nil},
		{DISABLED_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384, 32, 48, 16, ecdheRSAKA,
			suiteECDHE | suiteTLS12 | suiteSHA384, cipherAES, utlsMacSHA384, nil},
	}...)
}