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Cloak
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Fix padding calculation

This commit is contained in:
Andy Wang 2023-04-23 15:09:35 +02:00
parent bc67074610
commit d04366ec32
No known key found for this signature in database
GPG Key ID: 181B49F9F38F3374
2 changed files with 12 additions and 10 deletions
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21
internal/client/chrome.go
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@ -4,9 +4,8 @@ package client
import (
"encoding/binary"
"math/rand"
"github.com/cbeuw/Cloak/internal/common"
"math/rand"
)
type Chrome struct{}
@ -49,8 +48,9 @@ func (c *Chrome) composeExtensions(serverName string, keyShare []byte) []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] })
source := rand.NewSource(seed)
r := rand.New(source)
r.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
@ -58,7 +58,8 @@ func (c *Chrome) composeExtensions(serverName string, keyShare []byte) []byte {
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[1] = addExtRec([]byte{0x00, 0x00}, generateSNI(serverName)) // server name indication
sniLen := len(ext[1])
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
@ -80,12 +81,12 @@ func (c *Chrome) composeExtensions(serverName string, keyShare []byte) []byte {
shuffle(ext[1:16])
ext[16] = addExtRec(makeGREASE(), []byte{0x00}) // Last GREASE
// len(ext[1]) + len(all other ext) + len(ext[17]) = 403
// sniLen + 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
// len(ext[17]) = 228 - sniLen
// 2+2+len(padding) = 228 - sniLen
// len(padding) = 224 - sniLen
ext[17] = addExtRec([]byte{0x00, 0x15}, make([]byte, 224-sniLen)) // padding
var ret []byte
for _, e := range ext {
ret = append(ret, e...)

1
internal/client/chrome_test.go
View File

@ -34,6 +34,7 @@ func TestMakeGREASE(t *testing.T) {
func TestChromeJA3(t *testing.T) {
result := common.AddRecordLayer((&Chrome{}).composeClientHello(hd), common.Handshake, common.VersionTLS11)
assert.Equal(t, 517, len(result))
hello := tlsx.ClientHelloBasic{}
err := hello.Unmarshal(result)