Cloak/internal/client/firefox.go
2020-01-24 16:44:29 +00:00

78 lines
3.3 KiB
Go

// Fingerprint of Firefox 68
package client
import (
"crypto/rand"
"encoding/binary"
"encoding/hex"
)
type Firefox struct{}
func (f *Firefox) composeExtensions(SNI []byte, keyShare []byte) []byte {
composeKeyShare := func(hidden []byte) []byte {
ret := make([]byte, 107)
ret[0], ret[1] = 0x00, 0x69 // length 105
ret[2], ret[3] = 0x00, 0x1d // group x25519
ret[4], ret[5] = 0x00, 0x20 // length 32
copy(ret[6:38], hidden)
ret[38], ret[39] = 0x00, 0x17 // group secp256r1
ret[40], ret[41] = 0x00, 0x41 // length 65
rand.Read(ret[42:107])
return ret
}
// extension length is always 399, and server name length is variable
var ext [14][]byte
ext[0] = addExtRec([]byte{0x00, 0x00}, SNI) // 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}, []byte{}) // Session tickets
APLN, _ := hex.DecodeString("000c02683208687474702f312e31")
ext[6] = addExtRec([]byte{0x00, 0x10}, APLN) // app layer proto negotiation
ext[7] = addExtRec([]byte{0x00, 0x05}, []byte{0x01, 0x00, 0x00, 0x00, 0x00}) // status request
ext[8] = addExtRec([]byte{0x00, 0x33}, composeKeyShare(keyShare)) // key share
suppVersions, _ := hex.DecodeString("080304030303020301")
ext[9] = addExtRec([]byte{0x00, 0x2b}, suppVersions) // supported versions
sigAlgo, _ := hex.DecodeString("001604030503060308040805080604010501060102030201")
ext[10] = addExtRec([]byte{0x00, 0x0d}, sigAlgo) // Signature Algorithms
ext[11] = addExtRec([]byte{0x00, 0x2d}, []byte{0x01, 0x01}) // psk key exchange modes
ext[12] = addExtRec([]byte{0x00, 0x1c}, []byte{0x40, 0x01}) // record size limit
// len(ext[0]) + 237 + 4 + len(padding) = 399
// len(padding) = 158 - len(ext[0])
ext[13] = addExtRec([]byte{0x00, 0x15}, make([]byte, 163-len(SNI))) // padding
var ret []byte
for _, e := range ext {
ret = append(ret, e...)
}
return ret
}
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, 0x24} // cipher suites length 36
cipherSuites, _ := hex.DecodeString("130113031302c02bc02fcca9cca8c02cc030c00ac009c013c01400330039002f0035000a")
clientHello[7] = cipherSuites // cipher suites
clientHello[8] = []byte{0x01} // compression methods length 1
clientHello[9] = []byte{0x00} // compression methods
clientHello[11] = f.composeExtensions(hd.sni, hd.x25519KeyShare)
clientHello[10] = []byte{0x00, 0x00} // extensions length
binary.BigEndian.PutUint16(clientHello[10], uint16(len(clientHello[11])))
var ret []byte
for _, c := range clientHello {
ret = append(ret, c...)
}
return ret
}