Update to Chrome and Firefox 112

1 year ago · 641f6b2a9c
parent 646a323065
commit 641f6b2a9c
6 changed files with 166 additions and 103 deletions
--- a/go.mod
+++ b/go.mod
@ -4,6 +4,8 @@ go 1.14

 require (
 	github.com/cbeuw/connutil v0.0.0-20200411215123-966bfaa51ee3
+	github.com/dreadl0ck/ja3 v1.0.4
+	github.com/dreadl0ck/tlsx v1.0.1-google-gopacket
 	github.com/gorilla/mux v1.8.0
 	github.com/gorilla/websocket v1.4.2
 	github.com/juju/ratelimit v1.0.1
--- a/go.sum
+++ b/go.sum
@ -3,9 +3,16 @@ github.com/cbeuw/connutil v0.0.0-20200411215123-966bfaa51ee3/go.mod h1:6jR2SzckG
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dreadl0ck/ja3 v1.0.4 h1:/2wao59Ezn8xBWxn8CVq8eRcPZHbhoTdX6fmg7tQtnw=
+github.com/dreadl0ck/ja3 v1.0.4/go.mod h1:jATodgf1qBzTGieskRF2O1DXEwDgzEdqQjVcMMrCNpI=
+github.com/dreadl0ck/tlsx v1.0.1-google-gopacket h1:/P3y+CGRiCQbW0nZU2jWkEwKfXLkpEgHNhbbqlnrTTM=
+github.com/dreadl0ck/tlsx v1.0.1-google-gopacket/go.mod h1:amAb73WEEgPHWniMfwro6UpN6St3e5ypgq2tXM89IOo=
 github.com/dsnet/compress v0.0.1 h1:PlZu0n3Tuv04TzpfPbrnI0HW/YwodEXDS+oPKahKF0Q=
 github.com/dsnet/compress v0.0.1/go.mod h1:Aw8dCMJ7RioblQeTqt88akK31OvO8Dhf5JflhBbQEHo=
 github.com/dsnet/golib v0.0.0-20171103203638-1ea166775780/go.mod h1:Lj+Z9rebOhdfkVLjJ8T6VcRQv3SXugXy999NBtR9aFY=
+github.com/google/gopacket v1.1.17/go.mod h1:UdDNZ1OO62aGYVnPhxT1U6aI7ukYtA/kB8vaU0diBUM=
+github.com/google/gopacket v1.1.18 h1:lum7VRA9kdlvBi7/v2p7/zcbkduHaCH/SVVyurs7OpY=
+github.com/google/gopacket v1.1.18/go.mod h1:UdDNZ1OO62aGYVnPhxT1U6aI7ukYtA/kB8vaU0diBUM=
 github.com/gorilla/mux v1.8.0 h1:i40aqfkR1h2SlN9hojwV5ZA91wcXFOvkdNIeFDP5koI=
 github.com/gorilla/mux v1.8.0/go.mod h1:DVbg23sWSpFRCP0SfiEN6jmj59UnW/n46BH5rLB71So=
 github.com/gorilla/websocket v1.4.2 h1:+/TMaTYc4QFitKJxsQ7Yye35DkWvkdLcvGKqM+x0Ufc=
@ -37,18 +44,24 @@ go.etcd.io/bbolt v1.3.6 h1:/ecaJf0sk1l4l6V4awd65v2C3ILy7MSj+s/x1ADCIMU=
 go.etcd.io/bbolt v1.3.6/go.mod h1:qXsaaIqmgQH0T+OPdb99Bf+PKfBBQVAdyD6TY9G8XM4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20190325154230-a5d413f7728c/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20200221231518-2aa609cf4a9d/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/crypto v0.1.0 h1:MDRAIl0xIo9Io2xV565hzXHw3zVseKrJKodhohM5CjU=
 golang.org/x/crypto v0.1.0/go.mod h1:RecgLatLF4+eUMCP1PoPZQb+cVrJcOPbHkTkbkB9sbw=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
 golang.org/x/net v0.0.0-20190328230028-74de082e2cca/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
+golang.org/x/net v0.1.0 h1:hZ/3BUoy5aId7sCpA/Tc5lt8DkFgdVS2onTpJsZ/fl0=
 golang.org/x/net v0.1.0/go.mod h1:Cx3nUiGt4eDBEyega/BKRp+/AlGL8hYe7U9odMt2Cco=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190405154228-4b34438f7a67/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190804053845-51ab0e2deafa/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200923182605-d9f96fdee20d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
--- a/internal/client/chrome.go
+++ b/internal/client/chrome.go
@ -1,10 +1,10 @@
-// Fingerprint of Chrome 99
+// Fingerprint of Chrome 112

 package client

 import (
 	"encoding/binary"
-	"encoding/hex"
+	"math/rand"

 	"github.com/cbeuw/Cloak/internal/common"
 )
@ -45,33 +45,44 @@ func (c *Chrome) composeExtensions(serverName string, keyShare []byte) []byte {
 		return ret
 	}

-	// extension length is always 403, and server name length is variable
+	shuffle := func(exts [][]byte) {
+		var qword [8]byte
+		common.CryptoRandRead(qword[:])
+		seed := int64(binary.BigEndian.Uint64(qword[:]))
+		rand.Seed(seed)
+		rand.Shuffle(len(exts), func(i, j int) { exts[i], exts[j] = exts[j], exts[i] })
+	}

+	// extension length is always 403, and server name length is variable
 	var ext [18][]byte
-	ext[0] = addExtRec(makeGREASE(), nil)                           // First GREASE
-	ext[1] = addExtRec([]byte{0x00, 0x00}, generateSNI(serverName)) // server name indication
-	ext[2] = addExtRec([]byte{0x00, 0x17}, nil)                     // extended_master_secret
-	ext[3] = addExtRec([]byte{0xff, 0x01}, []byte{0x00})            // renegotiation_info
-	ext[4] = addExtRec([]byte{0x00, 0x0a}, makeSupportedGroups())   // supported groups
-	ext[5] = addExtRec([]byte{0x00, 0x0b}, []byte{0x01, 0x00})      // ec point formats
-	ext[6] = addExtRec([]byte{0x00, 0x23}, nil)                     // Session tickets
-	ALPN, _ := hex.DecodeString("000c02683208687474702f312e31")
-	ext[7] = addExtRec([]byte{0x00, 0x10}, ALPN)                                 // app layer proto negotiation
-	ext[8] = addExtRec([]byte{0x00, 0x05}, []byte{0x01, 0x00, 0x00, 0x00, 0x00}) // status request
-	sigAlgo, _ := hex.DecodeString("001004030804040105030805050108060601")
-	ext[9] = addExtRec([]byte{0x00, 0x0d}, sigAlgo)                 // Signature Algorithms
-	ext[10] = addExtRec([]byte{0x00, 0x12}, nil)                    // signed cert timestamp
-	ext[11] = addExtRec([]byte{0x00, 0x33}, makeKeyShare(keyShare)) // key share
-	ext[12] = addExtRec([]byte{0x00, 0x2d}, []byte{0x01, 0x01})     // psk key exchange modes
-	suppVersions, _ := hex.DecodeString("069A9A03040303")           // 9A9A needs to be a GREASE
+	ext[0] = addExtRec(makeGREASE(), nil) // First GREASE
+
+	// Start shufflable extensions: https://chromestatus.com/feature/5124606246518784
+	ext[1] = addExtRec([]byte{0x00, 0x00}, generateSNI(serverName))                           // server name indication
+	ext[2] = addExtRec([]byte{0x00, 0x17}, nil)                                               // extended_master_secret
+	ext[3] = addExtRec([]byte{0xff, 0x01}, []byte{0x00})                                      // renegotiation_info
+	ext[4] = addExtRec([]byte{0x00, 0x0a}, makeSupportedGroups())                             // supported groups
+	ext[5] = addExtRec([]byte{0x00, 0x0b}, []byte{0x01, 0x00})                                // ec point formats
+	ext[6] = addExtRec([]byte{0x00, 0x23}, nil)                                               // Session tickets
+	ext[7] = addExtRec([]byte{0x00, 0x10}, decodeHex("000c02683208687474702f312e31"))         // app layer proto negotiation
+	ext[8] = addExtRec([]byte{0x00, 0x05}, []byte{0x01, 0x00, 0x00, 0x00, 0x00})              // status request
+	ext[9] = addExtRec([]byte{0x00, 0x0d}, decodeHex("001004030804040105030805050108060601")) // Signature Algorithms
+	ext[10] = addExtRec([]byte{0x00, 0x12}, nil)                                              // signed cert timestamp
+	ext[11] = addExtRec([]byte{0x00, 0x33}, makeKeyShare(keyShare))                           // key share
+	ext[12] = addExtRec([]byte{0x00, 0x2d}, []byte{0x01, 0x01})                               // psk key exchange modes
+	suppVersions := decodeHex("069A9A03040303")                                               // 9A9A needs to be a GREASE
 	copy(suppVersions[1:3], makeGREASE())
 	ext[13] = addExtRec([]byte{0x00, 0x2b}, suppVersions)             // supported versions
 	ext[14] = addExtRec([]byte{0x00, 0x1b}, []byte{0x02, 0x00, 0x02}) // compress certificate
-	applicationSettings, _ := hex.DecodeString("0003026832")
-	ext[15] = addExtRec([]byte{0x44, 0x69}, applicationSettings) // application settings
-	ext[16] = addExtRec(makeGREASE(), []byte{0x00})              // Last GREASE
-	// len(ext[1]) + 175 + len(ext[16]) = 403
-	// len(ext[16]) = 228 - len(ext[1])
+	ext[15] = addExtRec([]byte{0x44, 0x69}, decodeHex("0003026832"))  // application settings
+	// End shufflable extensions
+
+	shuffle(ext[1:16])
+
+	ext[16] = addExtRec(makeGREASE(), []byte{0x00}) // Last GREASE
+	// len(ext[1]) + len(all other ext) + len(ext[17]) = 403
+	// len(all other ext) = 175
+	// len(ext[17]) = 228 - len(ext[1])
 	// 2+2+len(padding) = 228 - len(ext[1])
 	// len(padding) = 224 - len(ext[1])
 	ext[17] = addExtRec([]byte{0x00, 0x15}, make([]byte, 224-len(ext[1]))) // padding
@ -84,20 +95,22 @@ func (c *Chrome) composeExtensions(serverName string, keyShare []byte) []byte {

 func (c *Chrome) composeClientHello(hd clientHelloFields) (ch []byte) {
 	var clientHello [12][]byte
-	clientHello[0] = []byte{0x01}             // handshake type
-	clientHello[1] = []byte{0x00, 0x01, 0xfc} // length 508
-	clientHello[2] = []byte{0x03, 0x03}       // client version
-	clientHello[3] = hd.random                // random
-	clientHello[4] = []byte{0x20}             // session id length 32
-	clientHello[5] = hd.sessionId             // session id
-	clientHello[6] = []byte{0x00, 0x20}       // cipher suites length 32
-	cipherSuites, _ := hex.DecodeString("130113021303c02bc02fc02cc030cca9cca8c013c014009c009d002f0035")
-	clientHello[7] = append(makeGREASE(), cipherSuites...) // cipher suites
-	clientHello[8] = []byte{0x01}                          // compression methods length 1
-	clientHello[9] = []byte{0x00}                          // compression methods
-	clientHello[11] = c.composeExtensions(hd.serverName, hd.x25519KeyShare)
-	clientHello[10] = []byte{0x00, 0x00} // extensions length 403
-	binary.BigEndian.PutUint16(clientHello[10], uint16(len(clientHello[11])))
+	clientHello[0] = []byte{0x01}                                                                                       // handshake type
+	clientHello[1] = []byte{0x00, 0x01, 0xfc}                                                                           // length 508
+	clientHello[2] = []byte{0x03, 0x03}                                                                                 // client version
+	clientHello[3] = hd.random                                                                                          // random
+	clientHello[4] = []byte{0x20}                                                                                       // session id length 32
+	clientHello[5] = hd.sessionId                                                                                       // session id
+	clientHello[6] = []byte{0x00, 0x20}                                                                                 // cipher suites length 32
+	clientHello[7] = append(makeGREASE(), decodeHex("130113021303c02bc02fc02cc030cca9cca8c013c014009c009d002f0035")...) // cipher suites
+	clientHello[8] = []byte{0x01}                                                                                       // compression methods length 1
+	clientHello[9] = []byte{0x00}                                                                                       // compression methods
+
+	extensions := c.composeExtensions(hd.serverName, hd.x25519KeyShare)
+	clientHello[10] = []byte{0x00, 0x00}
+	binary.BigEndian.PutUint16(clientHello[10], uint16(len(extensions))) // extension length
+	clientHello[11] = extensions
+
 	var ret []byte
 	for _, c := range clientHello {
 		ret = append(ret, c...)
--- a/internal/client/chrome_test.go
+++ b/internal/client/chrome_test.go
@ -2,6 +2,12 @@ package client

 import (
 	"encoding/hex"
+	"github.com/cbeuw/Cloak/internal/common"
+	"github.com/dreadl0ck/ja3"
+	"github.com/dreadl0ck/tlsx"
+	"github.com/stretchr/testify/assert"
+	"sort"
+	"strings"
 	"testing"
 )

@ -26,21 +32,34 @@ func TestMakeGREASE(t *testing.T) {
 	}
 }

-func TestComposeExtension(t *testing.T) {
-	serverName := "github.com"
-	keyShare, _ := hex.DecodeString("690f074f5c01756982269b66d58c90c47dc0f281d654c7b2c16f63c9033f5604")
-
-	result := (&Chrome{}).composeExtensions(serverName, keyShare)
-	target, _ := hex.DecodeString("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")
-	for p := 0; p < len(result); p++ {
-		if result[p] != target[p] {
-			if result[p]&0x0F == 0xA && target[p]&0x0F == 0xA &&
-				((p > 0 && result[p-1] == result[p] && target[p-1] == target[p]) ||
-					(p < len(result)-1 && result[p+1] == result[p] && target[p+1] == target[p])) {
-				continue
-			}
-			t.Errorf("inequality at %v", p)
-		}
-	}
+func TestChromeJA3(t *testing.T) {
+	result := common.AddRecordLayer((&Chrome{}).composeClientHello(hd), common.Handshake, common.VersionTLS11)
+
+	hello := tlsx.ClientHelloBasic{}
+	err := hello.Unmarshal(result)
+	assert.Nil(t, err)

+	// Chrome shuffles the order of extensions, so it needs special handling
+	full := string(ja3.Bare(&hello))
+	// TLSVersion,Ciphers,Extensions,EllipticCurves,EllipticCurvePointFormats
+	parts := strings.Split(full, ",")
+
+	// TLSVersion,Ciphers
+	assert.Equal(t,
+		[]string{
+			"771",
+			"4865-4866-4867-49195-49199-49196-49200-52393-52392-49171-49172-156-157-47-53",
+		}, parts[0:2])
+	// EllipticCurves,EllipticCurvePointFormats
+	assert.Equal(t,
+		[]string{
+			"29-23-24", "0",
+		}, parts[3:5])
+
+	normaliseExtensions := func(extensions string) []string {
+		extensionParts := strings.Split(parts[2], "-")
+		sort.Strings(extensionParts)
+		return extensionParts
+	}
+	assert.Equal(t, normaliseExtensions("10-5-45-0-17513-13-18-11-23-16-35-27-65281-43-51-21"), normaliseExtensions(parts[2]))
 }
--- a/internal/client/firefox.go
+++ b/internal/client/firefox.go
@ -1,11 +1,9 @@
-// Fingerprint of Firefox 99
+// Fingerprint of Firefox 112

 package client

 import (
 	"encoding/binary"
-	"encoding/hex"
-
 	"github.com/cbeuw/Cloak/internal/common"
 )

@ -24,29 +22,24 @@ func (f *Firefox) composeExtensions(serverName string, keyShare []byte) []byte {
 		return ret
 	}
 	// extension length is always 401, and server name length is variable
-	var ext [15][]byte
-	ext[0] = addExtRec([]byte{0x00, 0x00}, generateSNI(serverName)) // server name indication
-	ext[1] = addExtRec([]byte{0x00, 0x17}, nil)                     // extended_master_secret
-	ext[2] = addExtRec([]byte{0xff, 0x01}, []byte{0x00})            // renegotiation_info
-	suppGroup, _ := hex.DecodeString("000c001d00170018001901000101")
-	ext[3] = addExtRec([]byte{0x00, 0x0a}, suppGroup)          // supported groups
-	ext[4] = addExtRec([]byte{0x00, 0x0b}, []byte{0x01, 0x00}) // ec point formats
-	ext[5] = addExtRec([]byte{0x00, 0x23}, nil)                // session ticket
-	ALPN, _ := hex.DecodeString("000c02683208687474702f312e31")
-	ext[6] = addExtRec([]byte{0x00, 0x10}, ALPN)                                 // app layer proto negotiation
-	ext[7] = addExtRec([]byte{0x00, 0x05}, []byte{0x01, 0x00, 0x00, 0x00, 0x00}) // status request
-	delegatedCredentials, _ := hex.DecodeString("00080403050306030203")
-	ext[8] = addExtRec([]byte{0x00, 0x22}, delegatedCredentials)      // delegated credentials
-	ext[9] = addExtRec([]byte{0x00, 0x33}, composeKeyShare(keyShare)) // key share
-	suppVersions, _ := hex.DecodeString("0403040303")
-	ext[10] = addExtRec([]byte{0x00, 0x2b}, suppVersions) // supported versions
-	sigAlgo, _ := hex.DecodeString("001604030503060308040805080604010501060102030201")
-	ext[11] = addExtRec([]byte{0x00, 0x0d}, sigAlgo)            // Signature Algorithms
-	ext[12] = addExtRec([]byte{0x00, 0x2d}, []byte{0x01, 0x01}) // psk key exchange modes
-	ext[13] = addExtRec([]byte{0x00, 0x1c}, []byte{0x40, 0x01}) // record size limit
-	// len(ext[0]) + 238 + 4 + len(padding) = 401
-	// len(padding) = 177 - len(ext[0])
-	ext[14] = addExtRec([]byte{0x00, 0x15}, make([]byte, 159-len(ext[0]))) // padding
+	var ext [13][]byte
+	ext[0] = addExtRec([]byte{0x00, 0x00}, generateSNI(serverName))                                        // server name indication
+	ext[1] = addExtRec([]byte{0x00, 0x17}, nil)                                                            // extended_master_secret
+	ext[2] = addExtRec([]byte{0xff, 0x01}, []byte{0x00})                                                   // renegotiation_info
+	ext[3] = addExtRec([]byte{0x00, 0x0a}, decodeHex("000c001d00170018001901000101"))                      // supported groups
+	ext[4] = addExtRec([]byte{0x00, 0x0b}, []byte{0x01, 0x00})                                             // ec point formats
+	ext[5] = addExtRec([]byte{0x00, 0x10}, decodeHex("000c02683208687474702f312e31"))                      // app layer proto negotiation
+	ext[6] = addExtRec([]byte{0x00, 0x05}, []byte{0x01, 0x00, 0x00, 0x00, 0x00})                           // status request
+	ext[7] = addExtRec([]byte{0x00, 0x22}, decodeHex("00080403050306030203"))                              // delegated credentials
+	ext[8] = addExtRec([]byte{0x00, 0x33}, composeKeyShare(keyShare))                                      // key share
+	ext[9] = addExtRec([]byte{0x00, 0x2b}, decodeHex("0403040303"))                                        // supported versions
+	ext[10] = addExtRec([]byte{0x00, 0x0d}, decodeHex("001604030503060308040805080604010501060102030201")) // Signature Algorithms
+	ext[11] = addExtRec([]byte{0x00, 0x1c}, []byte{0x40, 0x01})                                            // record size limit
+	// len(ext[0]) + len(all other ext) + len(len field of padding) + len(padding) = 401
+	// len(all other ext) = 228
+	// len(len field of padding) = 4
+	// len(padding) = 169 - len(ext[0])
+	ext[12] = addExtRec([]byte{0x00, 0x15}, make([]byte, 169-len(ext[0]))) // padding
 	var ret []byte
 	for _, e := range ext {
 		ret = append(ret, e...)
@ -56,21 +49,21 @@ func (f *Firefox) composeExtensions(serverName string, keyShare []byte) []byte {

 func (f *Firefox) composeClientHello(hd clientHelloFields) (ch []byte) {
 	var clientHello [12][]byte
-	clientHello[0] = []byte{0x01}             // handshake type
-	clientHello[1] = []byte{0x00, 0x01, 0xfc} // length 508
-	clientHello[2] = []byte{0x03, 0x03}       // client version
-	clientHello[3] = hd.random                // random
-	clientHello[4] = []byte{0x20}             // session id length 32
-	clientHello[5] = hd.sessionId             // session id
-	clientHello[6] = []byte{0x00, 0x22}       // cipher suites length 34
-	cipherSuites, _ := hex.DecodeString("130113031302c02bc02fcca9cca8c02cc030c00ac009c013c014009c009d002f0035")
-	clientHello[7] = cipherSuites // cipher suites
-	clientHello[8] = []byte{0x01} // compression methods length 1
-	clientHello[9] = []byte{0x00} // compression methods
+	clientHello[0] = []byte{0x01}                                                                      // handshake type
+	clientHello[1] = []byte{0x00, 0x01, 0xfc}                                                          // length 508
+	clientHello[2] = []byte{0x03, 0x03}                                                                // client version
+	clientHello[3] = hd.random                                                                         // random
+	clientHello[4] = []byte{0x20}                                                                      // session id length 32
+	clientHello[5] = hd.sessionId                                                                      // session id
+	clientHello[6] = []byte{0x00, 0x22}                                                                // cipher suites length 34
+	clientHello[7] = decodeHex("130113031302c02bc02fcca9cca8c02cc030c00ac009c013c014009c009d002f0035") // cipher suites
+	clientHello[8] = []byte{0x01}                                                                      // compression methods length 1
+	clientHello[9] = []byte{0x00}                                                                      // compression methods

-	clientHello[11] = f.composeExtensions(hd.serverName, hd.x25519KeyShare)
-	clientHello[10] = []byte{0x00, 0x00} // extensions length
-	binary.BigEndian.PutUint16(clientHello[10], uint16(len(clientHello[11])))
+	extensions := f.composeExtensions(hd.serverName, hd.x25519KeyShare)
+	clientHello[10] = []byte{0x00, 0x00}
+	binary.BigEndian.PutUint16(clientHello[10], uint16(len(extensions))) // extension length
+	clientHello[11] = extensions

 	var ret []byte
 	for _, c := range clientHello {
--- a/internal/client/firefox_test.go
+++ b/internal/client/firefox_test.go
@ -1,20 +1,43 @@
 package client

 import (
-	"bytes"
 	"encoding/hex"
+	"github.com/cbeuw/Cloak/internal/common"
+	"github.com/dreadl0ck/ja3"
+	"github.com/dreadl0ck/tlsx"
+	"github.com/stretchr/testify/assert"
+	"strings"
 	"testing"
 )

-func TestComposeExtensions(t *testing.T) {
-	target, _ := hex.DecodeString("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")
+var hd = clientHelloFields{
+	random:         decodeHex("ed0117085ed70be0799b1fc96af7f675d4747f86cd03bb36392e03e8d1b0e9a0"),
+	sessionId:      decodeHex("47485f67c59ca787009bba83ede4da4f2397169c696c275d96c4c7af803019b9"),
+	x25519KeyShare: decodeHex("d395003163a6f751b4c68a67bcec1f883885a7ada8a63fda389b29986e51fa44"),
+	serverName:     "github.com",
+}
+
+func TestFirefoxJA3(t *testing.T) {
+	result := common.AddRecordLayer((&Firefox{}).composeClientHello(hd), common.Handshake, common.VersionTLS11)

-	serverName := "consent.google.com"
-	keyShare, _ := hex.DecodeString("8d8ea1b80430b7710b65f0d89b0144a5eeb218709ce6613d4fc8bfb117657c15")
+	hello := tlsx.ClientHelloBasic{}
+	err := hello.Unmarshal(result)
+	assert.Nil(t, err)
+
+	digest := ja3.DigestHex(&hello)
+	assert.Equal(t, "ad55557b7cbd735c2627f7ebb3b3d493", digest)
+}
+
+func TestFirefoxComposeClientHello(t *testing.T) {
+	result := hex.EncodeToString((&Firefox{}).composeClientHello(hd))
+	target := "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"

-	result := (&Firefox{}).composeExtensions(serverName, keyShare)
 	// skip random secp256r1
-	if !bytes.Equal(result[:151], target[:151]) || !bytes.Equal(result[216:], target[216:]) {
-		t.Errorf("got %x", result)
-	}
+	secp256r1 := "04c49751010e35370cf8e89c23471b40579387b3dd5ce6862c9850b121632b527128b75ef7051c5284ae94894d846cc3dc88ce01ce49b605167f63473c1d772b47"
+	start := strings.Index(target, secp256r1)
+
+	target = strings.Replace(target, secp256r1, "", 1)
+	result = strings.Replace(result, result[start:start+len(secp256r1)], "", 1)
+
+	assert.Equal(t, target, result)
 }