Cloak/internal/client/chrome.go
2020-04-05 00:56:43 +01:00

104 lines
4.2 KiB
Go

// Fingerprint of Chrome 76
package client
import (
"encoding/binary"
"encoding/hex"
"github.com/cbeuw/Cloak/internal/util"
)
type Chrome struct{}
func makeGREASE() []byte {
// see https://tools.ietf.org/html/draft-davidben-tls-grease-01
// This is exclusive to Chrome.
var one [1]byte
util.CryptoRandRead(one[:])
sixteenth := one[0] % 16
monoGREASE := sixteenth*16 + 0xA
doubleGREASE := []byte{monoGREASE, monoGREASE}
return doubleGREASE
}
func (c *Chrome) composeExtensions(sni []byte, keyShare []byte) []byte {
makeSupportedGroups := func() []byte {
suppGroupListLen := []byte{0x00, 0x08}
ret := make([]byte, 2+8)
copy(ret[0:2], suppGroupListLen)
copy(ret[2:4], makeGREASE())
copy(ret[4:], []byte{0x00, 0x1d, 0x00, 0x17, 0x00, 0x18})
return ret
}
makeKeyShare := func(hidden []byte) []byte {
ret := make([]byte, 43)
ret[0], ret[1] = 0x00, 0x29 // length 41
copy(ret[2:4], makeGREASE())
ret[4], ret[5] = 0x00, 0x01 // length 1
ret[6] = 0x00
ret[7], ret[8] = 0x00, 0x1d // group x25519
ret[9], ret[10] = 0x00, 0x20 // length 32
copy(ret[11:43], hidden)
return ret
}
// extension length is always 401, and server name length is variable
var ext [17][]byte
ext[0] = addExtRec(makeGREASE(), nil) // First GREASE
ext[1] = addExtRec([]byte{0x00, 0x00}, sni) // 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
APLN, _ := hex.DecodeString("000c02683208687474702f312e31")
ext[7] = addExtRec([]byte{0x00, 0x10}, APLN) // app layer proto negotiation
ext[8] = addExtRec([]byte{0x00, 0x05}, []byte{0x01, 0x00, 0x00, 0x00, 0x00}) // status request
sigAlgo, _ := hex.DecodeString("0012040308040401050308050501080606010201")
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("0a9A9A0304030303020301") // 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})
ext[15] = addExtRec(makeGREASE(), []byte{0x00}) // Last GREASE
// len(ext[1]) + 172 + len(ext[16]) = 401
// len(ext[16]) = 229 - len(ext[1])
// 2+2+len(padding) = 229 - len(ext[1])
// len(padding) = 225 - len(ext[1])
ext[16] = addExtRec([]byte{0x00, 0x15}, make([]byte, 225-len(ext[1]))) // padding
var ret []byte
for _, e := range ext {
ret = append(ret, e...)
}
return ret
}
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, 0x22} // cipher suites length 34
cipherSuites, _ := hex.DecodeString("130113021303c02bc02fc02cc030cca9cca8c013c014009c009d002f0035000a")
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.sni, hd.x25519KeyShare)
clientHello[10] = []byte{0x00, 0x00} // extensions length 401
binary.BigEndian.PutUint16(clientHello[10], uint16(len(clientHello[11])))
var ret []byte
for _, c := range clientHello {
ret = append(ret, c...)
}
return ret
}