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Cloak
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Refactor client ClientHello composition

This commit is contained in:
Andy Wang 2019-08-17 00:16:31 +01:00
parent b5c6d7fedc
commit b98a74f49b
6 changed files with 46 additions and 42 deletions
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14
internal/client/TLS.go
View File

@ -9,7 +9,7 @@ import (
)
type Browser interface {
composeClientHello(*State) ([]byte, []byte)
composeClientHello(chHiddenData) []byte
}
func makeServerName(serverName string) []byte {
@ -37,15 +37,11 @@ func addExtRec(typ []byte, data []byte) []byte {
return ret
}
// composeClientHello composes ClientHello with record layer
func composeClientHello(sta *State) ([]byte, []byte) {
ch, sharedSecret := sta.Browser.composeClientHello(sta)
return util.AddRecordLayer(ch, []byte{0x16}, []byte{0x03, 0x01}), sharedSecret
}
func PrepareConnection(sta *State, conn net.Conn) (sessionKey []byte, err error) {
clientHello, sharedSecret := composeClientHello(sta)
_, err = conn.Write(clientHello)
hd, sharedSecret := makeHiddenData(sta)
chOnly := sta.Browser.composeClientHello(hd)
chWithRecordLayer := util.AddRecordLayer(chOnly, []byte{0x16}, []byte{0x03, 0x01})
_, err = conn.Write(chWithRecordLayer)
if err != nil {
return
}

18
internal/client/auth.go
View File

@ -12,11 +12,18 @@ const (
UNORDERED_FLAG = 0x01 // 0000 0001
)
func makeHiddenData(sta *State) (random, TLSsessionID, keyShare, sharedSecret []byte) {
type chHiddenData struct {
chRandom []byte
chSessionId []byte
chX25519KeyShare []byte
chExtSNI []byte
}
func makeHiddenData(sta *State) (ret chHiddenData, sharedSecret []byte) {
// random is marshalled ephemeral pub key 32 bytes
// TLSsessionID || keyShare is [encrypted UID 16 bytes, proxy method 12 bytes, encryption method 1 byte, timestamp 8 bytes, sessionID 4 bytes] [1 byte flag] [6 bytes reserved] [16 bytes authentication tag]
ephPv, ephPub, _ := ecdh.GenerateKey(rand.Reader)
random = ecdh.Marshal(ephPub)
ret.chRandom = ecdh.Marshal(ephPub)
plaintext := make([]byte, 48)
copy(plaintext, sta.UID)
@ -30,9 +37,10 @@ func makeHiddenData(sta *State) (random, TLSsessionID, keyShare, sharedSecret []
}
sharedSecret = ecdh.GenerateSharedSecret(ephPv, sta.staticPub)
nonce := random[0:12]
nonce := ret.chRandom[0:12]
ciphertext, _ := util.AESGCMEncrypt(nonce, sharedSecret, plaintext)
TLSsessionID = ciphertext[0:32]
keyShare = ciphertext[32:64]
ret.chSessionId = ciphertext[0:32]
ret.chX25519KeyShare = ciphertext[32:64]
ret.chExtSNI = makeServerName(sta.ServerName)
return
}

15
internal/client/chrome.go
View File

@ -21,7 +21,7 @@ func makeGREASE() []byte {
return doubleGREASE
}
func (c *Chrome) composeExtensions(serverName string, keyShare []byte) []byte {
func (c *Chrome) composeExtensions(sni []byte, keyShare []byte) []byte {
makeSupportedGroups := func() []byte {
suppGroupListLen := []byte{0x00, 0x08}
@ -48,7 +48,7 @@ func (c *Chrome) composeExtensions(serverName string, keyShare []byte) []byte {
var ext [17][]byte
ext[0] = addExtRec(makeGREASE(), nil) // First GREASE
ext[1] = addExtRec([]byte{0x00, 0x00}, makeServerName(serverName)) // server name indication
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
@ -79,26 +79,25 @@ func (c *Chrome) composeExtensions(serverName string, keyShare []byte) []byte {
return ret
}
func (c *Chrome) composeClientHello(sta *State) (ch []byte, sharedSecret []byte) {
random, sessionID, keyShare, sharedSecret := makeHiddenData(sta)
func (c *Chrome) composeClientHello(hd chHiddenData) (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] = random // random
clientHello[3] = hd.chRandom // random
clientHello[4] = []byte{0x20} // session id length 32
clientHello[5] = sessionID // session id
clientHello[5] = hd.chSessionId // 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(sta.ServerName, keyShare)
clientHello[11] = c.composeExtensions(hd.chExtSNI, hd.chX25519KeyShare)
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, sharedSecret
return ret
}

4
internal/client/chrome_test.go
View File

@ -30,7 +30,9 @@ func TestComposeExtension(t *testing.T) {
serverName := "cdn.bizible.com"
keyShare, _ := hex.DecodeString("010a8896b68fb16e2a245ed87be2699348ab72068bb326eac5beaa00fa56ff17")
result := (&Chrome{}).composeExtensions(serverName, keyShare)
sni := makeServerName(serverName)
result := (&Chrome{}).composeExtensions(sni, keyShare)
target, _ := hex.DecodeString("5a5a000000000014001200000f63646e2e62697a69626c652e636f6d00170000ff01000100000a000a0008fafa001d00170018000b00020100002300000010000e000c02683208687474702f312e31000500050100000000000d00140012040308040401050308050501080606010201001200000033002b0029fafa000100001d0020010a8896b68fb16e2a245ed87be2699348ab72068bb326eac5beaa00fa56ff17002d00020101002b000b0aaaaa0304030303020301001b0003020002eaea000100001500c9000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000")
for p := 0; p < len(result); {
// skip GREASEs

18
internal/client/firefox.go
View File

@ -9,7 +9,7 @@ import (
type Firefox struct{}
func (f *Firefox) composeExtensions(serverName string, keyShare []byte) []byte {
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
@ -23,7 +23,7 @@ func (f *Firefox) composeExtensions(serverName string, keyShare []byte) []byte {
}
// extension length is always 399, and server name length is variable
var ext [14][]byte
ext[0] = addExtRec([]byte{0x00, 0x00}, makeServerName(serverName)) // server name indication
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")
@ -42,7 +42,7 @@ func (f *Firefox) composeExtensions(serverName string, keyShare []byte) []byte {
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, 158-len(serverName))) // padding
ext[13] = addExtRec([]byte{0x00, 0x15}, make([]byte, 163-len(SNI))) // padding
var ret []byte
for _, e := range ext {
ret = append(ret, e...)
@ -50,23 +50,21 @@ func (f *Firefox) composeExtensions(serverName string, keyShare []byte) []byte {
return ret
}
func (f *Firefox) composeClientHello(sta *State) (ch []byte, sharedSecret []byte) {
random, sessionID, keyShare, sharedSecret := makeHiddenData(sta)
func (f *Firefox) composeClientHello(hd chHiddenData) (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] = random // random
clientHello[3] = hd.chRandom // random
clientHello[4] = []byte{0x20} // session id length 32
clientHello[5] = sessionID // session id
clientHello[5] = hd.chSessionId // 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(sta.ServerName, keyShare)
clientHello[11] = f.composeExtensions(hd.chExtSNI, hd.chX25519KeyShare)
clientHello[10] = []byte{0x00, 0x00} // extensions length
binary.BigEndian.PutUint16(clientHello[10], uint16(len(clientHello[11])))
@ -74,5 +72,5 @@ func (f *Firefox) composeClientHello(sta *State) (ch []byte, sharedSecret []byte
for _, c := range clientHello {
ret = append(ret, c...)
}
return ret, sharedSecret
return ret
}

3
internal/client/firefox_test.go
View File

@ -11,7 +11,8 @@ func TestComposeExtensions(t *testing.T) {
serverName := "consent.google.com"
keyShare, _ := hex.DecodeString("6075db0a43812b2e4e0f44157f04295b484ccfc6d70e577c1e6113aa18e08827")
result := (&Firefox{}).composeExtensions(serverName, keyShare)
sni := makeServerName(serverName)
result := (&Firefox{}).composeExtensions(sni, keyShare)
// skip random secp256r1
if !bytes.Equal(result[:137], target[:137]) || !bytes.Equal(result[202:], target[202:]) {
t.Errorf("got %x", result)